1. Field of the Invention
The present invention relates to a liquid crystal cell and liquid crystal display device using an antiferroelectric liquid crystal. The present invention is advantageously used for a liquid crystal TV, a liquid crystal watch, various display devices, etc.
2. Description of the Related Art
Recently, a liquid crystal cell has been widely used as a display element having many features, for example, thin configuration, light weight, and low power consumption. In general, almost all display elements are formed of TN (Twisted Nematic)-type liquid crystal cells which use nematic liquid crystals. The display method using the TN-type liquid crystal cell has a very slow response speed (time). This is because the liquid crystal cell is driven based on an anisotropic characteristic of a dielectric constant of the liquid crystal. Accordingly, it has been required to improve the response speed in the TN type liquid crystal.
On the other hand, another liquid crystal cell, which uses the liquid crystal having a chiral smectic C phase (below, SmC* phase) indicating a ferroelectric characteristic (this type of liquid crystal was found by Mr. Meyer et al.), has a high response speed and a good storage characteristic which could not be achieved by the above nematic liquid crystal. Accordingly, recently, research and development have been performed to discover a ferroelectric liquid crystal cell having the above good characteristics.
However, it is very difficult to realize good molecular alignment of liquid crystal molecules and good storage characteristic, both of which are necessary for providing a good display with the above-described liquid crystal cell, because this type of liquid crystal cell is easily damaged by a shock applied from outside.
Further, recently, in the liquid crystal having the SmC* phase, an antiferroelectric phase (SmC.sub.A * phase), which has three stable states at the low temperature of the SmC* phase, was found by Ms. Chandani et al.
In the SMC.sub.A * phase, dipoles (i.e., liquid crystal molecules) are arranged in anti-parallel for an adjacent layer (i.e., as shown in FIG. 4 dipoles are arranged in parallel in the same layer, but not arranged in parallel for the adjacent layer), and this arrangement indicates a thermodynamically stable state. Further, in the SmC.sub.A * phase, there is an electric field-induced phase transition between the antiferroelectric phase and the ferroelectric phase, and this electric field-induced phase transition features a double hysteresis characteristic (i.e., switching characteristic) and a threshold value for a supply voltage. As a result, research and development on the switching characteristic and threshold value have begun in order to obtain a new display method using the antiferroelectric liquid crystal cell.
Accordingly, the present invention aims to provide an improved liquid crystal cell and liquid crystal display device using an antiferroelectric liquid crystal.